Materials handling vehicles which are known and referred to as mobile high lift loaders are used for material handling jobs that require placing of a load in positions beyond the immediate area of the loader. For example, in construction jobs, it is desirable to lift heavy loads such as bricks and other materials and place them on floors within the building under construction which requires movement of the load high above and forward from the loader. For some purposes, it is necessary to reach to a level below that on which the loader rests. A reaching action is often necessary in the unloading of trucks or railroad cars, in the handling of lumber, logs, and the like.
Lull U.S. Pat. No. 3,198,359 discloses one type of reaching loader in which the ends of lift arms can be moved forward of the loader by means of a longitudinally movable carriage to which the lift arms are pivotally secured. This construction separates the reaching action from the raising and lowering action and eliminates many of the disadvantages of earlier loaders. However, the height to which loads may be lifted is limited by the length of the lift arms, and the distance of longitudinal transfer is limited relative to the length of the vehicle.
Goyarts U.S. Pat. No. 3,967,744 discloses a loader in which a load handling device is carried at the end of a boom which in turn is pivotally mounted on a trolley adapted to travel longitudinally along a second boom pivotally secured to the carrier vehicle. This type of loader permits reaching by virtue of the longitudinal travel of the trolley and permits some additional lifting height by virtue of the pivotal movement of the second boom relative to the vehicle. However, here too the lifting height is limited by virtue of the fixed length of the boom supporting the load lifting mechanism.
Lull U.S. Pat. No. 3,178,046 discloses a reaching loader in which the load carrying means is supported at the end of a telescopic boom pivotally secured to a vehicle. Extended reach is accomplished by extension of the telescopic boom, but both reach and lifting height are limited by the length of that boom.
Lull U.S. Pat. No. 4,147,263 discloses a loader having extended transfer with the load carrying means supported at the end of a telescopic boom which is pivotally secured to transfer means, preferably in the form of a transfer carriage. The transfer means can move the telescopic boom forward and rearward in addition to the reach attainable by extension, retraction, lifting and lowering of the boom.
Triple section telescopic booms are also generally known in the prior art. For example, Lull Model 1522 includes a triple section telescopic boom on a reaching loader wherein the boom is pivotally secured to directly to the vehicle. While an extended reach is accomplished by extension, retraction, lifting and lowering of the boom, the reach and lifting height are limited by the length of that boom and the vehicle must be substantially reinforced to prevent tipover when the boom is fully extended and carrying loads near its maximum weight handling capacity.
The present invention resolves the deficiencies of the prior art and provides a versatile, stable, variable reach rough terrain load lifting apparatus which is a substantial technological advance over existing devices.